There are 37 arcs in One Piece (anime) so far - Out of the 37, 31 are story arcs (ranging from 5 - 80 episodes in length that follow the manga to a "T") - Out of the 37, 6 are filler arcs (ranging from 2 - 13 episodes in length). Heck... The filler arcs are mostly comedic bits to ease tension buildup during story arcs.

It's better then Naruto, Fullmetal Alchemist (not Brotherhood) and Bleach, that really are 70% - 80% filler and don't follow the manga as they should.

You (Scott) also missed the part(s) where you see just how cruel the World Government is, and how they are trying to stop (by any means necessary) the discovery of the Void Century.

Quick (sloppy) summary:

Nico Robin hates the government because they destroyed her home island, with something called a Buster Call. Her island was nothing but scholars, one of which was her mother (a fugitive), who were trying to uncover the truth about the Void Century and why the World Government fears it so much. During the story arc(s) you missed, Nico Robin surrenders (voluntary) to a top secret government organization called CP9 at the city of Water 7, so that Luffy and crew wouldn't be executed. The World Government/CP9 wanted to capture Nico Robin for years, hence why she has a wanted post of as her a child, because she escaped the destruction of her home island and is getting closer and closer to discovering the mystery of the Void Century (she's the only one left able to read Poneglyphs).

So... Of course... Luffy doesn't like how Nico Robin is being treated like a "piece of meat", so him and crew (and the Franky Family), formulate a plan to rescue her from the judicial island of Enies Lobby (CP9's headquarters). Through lots of blood and sweat and tears, Luffy and crew overcome the various Devil Fruit empowered operatives of CP9 and rescue Nico Robin (while Buster Calling Enies Lobby in the process), finally making her a permanent member of his crew. Admiral Aokiji, who first appeared in the opening episode of the Water 7 and Enies Lobby story arcs, appears when the crew arrives back at Water 7 to celebrate their victory. He holds the Strawhat crew in somewhat high regard (despite being a leading marine) and asks Nico Robin "have found a place to call home", to which she answers "yes".